* Jianping Zhu
> I need to insert recond to mysql use servlets,
>
> insert into mytable values('key', 'f1');
>
> i need to chech if key is already in mytable.why? > what is a good efficient way to do that? The most obvious answer, do a lookup to check if the record exist: SELECT * FROM mytable WHERE key='key'; If you get no result, the record does not exist. However, there is a problem with this approach in a multiuser environment: what if a different user inserts this key a fraction of a second after you have found out it does not exist...? You would get an duplicate key error, and your program must be able to handle this. That is why it is normally better to just do the insert in the first place, and then check if the insert resulted in an error, which would indicate that the record already existed. -- Roger --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
